Anti-fogging surgical mask

Abstract

Surgical masks comprising: (a) a main body portion comprising a filter portion which comprises filter means divided into an upper region and a lower region, the lower region of the filter means being more permeable to air than the upper region of the filter means; (b) means for providing an effective seal between the upper edge of the main body portion and the nose of the wearer; (c) and means for securing the mask over the mouth and nose of the wearer. A preferred surgical mask comprises a filter means comprising two distinct filter webs of different permeabilities. These surgical masks function as effective filters to the passage of bacteria-containing liquid droplets and may be suitably worn by eye-glass clad operating room staff members since exhaled air, which could otherwise fog eyeglasses, is directed downward away from the eyes of the wearer of the mask. Furthermore, these surgical masks are comfortable to wear and may assume a comfortable, off-the-face or "duckbill" configuration.

What is claimed is: 
     
       1. An anti-fog surgical mask for covering at least the nose, mouth and a portion of the chin of the wearer, comprising: (a) a main body portion having an upper edge and a lower edge and comprising a filter portion between said upper edge and said lower edge, said filter portion comprising a filter means extending from about said upper edge to a location at about the chin of the wearer, said filter means divided into an upper region and a lower region, said upper region of said filter means being located at about said upper edge and providing between about 25 and 70 percent of the total area of said filter means, and said lower region of said filter means being adjacent to said upper region of said filter means and providing substantially the remainder of the total area of said filter means;   said filter means being further characterized in that said upper region and said lower region of said filter means are permeable substantially throughout, the average permeability of said upper region of said filter means is at least about 6 cubic feet of air per square foot per minute, and the average permeability of said lower region of said filter means is at least about 22.25 cubic feet of air per square foot per minute and is greater than the average permeability of said upper region of said filter means by at least about 2.25 cubic feet of air per square foot per minute, the permeabilities being measured in accordance with ASTM D 737-75 (Reapproved 1980) using a pressure differential of 0.5 inch of water across said filter means;   (b) means at said upper edge for providing an effective seal between said upper edge of said main body portion and the nose of the wearer; and   (c) means attached to said main body portion for securing said mask over the mouth and the nose of the wearer; said mask being substantially flexible and said upper region being oriented with respect to said lower region such that exhaled air is directed away from the eyes of the wearer of said mask in order to reduce the possibility of fogging eyeglasses.   
     
     
       2. An antifog surgical mask in accordance with claim 1, wherein said filter means comprises a single filter web. 
     
     
       3. An anti-fog surgical mask in accordance with claim 2, wherein said upper region of said filter means accounts for between about 45 and 55 percent of the total area of said filter means. 
     
     
       4. An anti-fog surgical mask in accordance with claim 2, wherein the average permeability of said upper region of said filter means is at least about 20 cubic feet of air per square foot per minute and the average permeability of said lower region of said filter means is greater than the average permeability of said upper region of said filter means by at least about 8 cubic feet of air per square foot per minute. 
     
     
       5. An anti-fog surgical mask in accordance with claim 4, wherein the average permeability of said lower region of said filter means is greater than the average permeability of said upper region by at least about 12 cubic feet of air per square foot per minute. 
     
     
       6. An anti-fog surgical mask comprising: (a) a main body portion having an upper edge and a lower edge and comprising a filter portion between said upper edge and said lower edge, said filter portion comprising a filter means extending from a location at about said upper edge to a location at about the chin of the wearer, said filter means divided into an upper region comprising an upper filter web and a lower region comprising a lower filter web, said upper filter web being located at about said upper edge, having a lower end, and providing between about 25 and 70 percent of the total area of said filter means, and said lower filter web having an upper end and providing substantially the remainder of the total area of said filter means, said upper filter web and said lower filter web being connected at said lower end of said upper filter web and said upper end of said lower filter web;   said filter means being further characterized in that said upper region and said lower region of said filter means are permeable substantially throughout, the permeabilities of said upper region and said lower region of said filter means are substantially uniform throughout each of said upper region and said lower region, the average permeability of said upper region of said filter means is at least about 6 cubic feet of air per square foot per minute, and the average permeability of said lower region of said filter means is at least about 22.25 cubic feet of air per square foot per minute and is greater than the average permeability of said upper region of said filter means by at least about 2.25 cubic feet of air per square foot per minute, the permeabilities being measured in accordance with ASTM D 737-75 (Reapproved 1980) using a pressure differential of 0.5 inch of water across said filter means;   (b) means at said upper edge for providing an effective seal between said upper edge of said main body portion and the nose of the wearer; and   (c) means attached to said main body portion for securing said mask over the mouth and the nose of the wearer; said mask being substantially flexible and said upper region being oriented with respect to said lower region such that exhaled air is directed away from the eyes of the wearer of said mask in order to reduce the possibility of fogging eyeglasses.   
     
     
       7. An anti-fog surgical mask in accordance with claim 6, wherein said upper region of said filter means provides between about 45 and 55 percent of the total area of said filter means. 
     
     
       8. An anti-fog surgical mask in accordance with claim 7, wherein the average permeability of said upper region of said filter means is at least about 20 cubic feet of air per square foot per minute and the average permeability of said lower region of said filter means is greater than the average permeability of said upper region of said filter means by at least 8 cubic feet of air per square foot per minute. 
     
     
       9. An anti-fog surgical mask in accordance with claim 6, wherein the average permeability of said upper region of said filter means is at least about 20 cubic feet of air per square foot per minute and the average permeability of said lower region of said filter means is greater than the average permeability of said upper region of said filter means by at least about 8 cubic feet of air per square foot per minute. 
     
     
       10. An anti-fog surgical mask in accordance with claim 9, wherein the average permeability of said lower region of said filter means is greater than the average permeability of said upper region of said filter means by at least 12 cubic feet of air per square foot per minute. 
     
     
       11. An anti-fog surgical mask in accordance with claim 6, wherein said upper filter web and said lower filter web comprise polypropylene and said lower filter web is electrically charged. 
     
     
       12. An anti-fog surgical mask in accordance with claim 6, further comprising cover webs situated on both sides of said filter means. 
     
     
       13. An anti-fog surgical mask in accordance with claim 6, wherein said surgical mask is an off-the-face surgical mask. 
     
     
       14. An anti-fog surgical mask in accordance with claim 6, wherein said filter portion extends beneath the chin of the wearer.